Electrical power supplied from an electric power system (e.g., a power grid) to a building fluctuates greatly depending on the operating status of machinery that use electric power (i.e., a load). In this regard, for buildings that consume a large amount of electric power such as factories, a storage battery equipment is often used to level, or reducing the peak of, the electric power supplied from the electric power system (e.g., refer to JP 2014-128063 A).
This type of storage battery equipment stores electric power in a storage battery during relatively low power consumption time bands (e.g., during the night), and supplies power from the storage battery during relatively high power consumption time bands. By using the storage battery equipment, a peak value of the electric power supplied from the electric power system may be kept low, and thus electricity fees paid to power companies may be reduced.
In order to interconnect the power supplied from storage battery equipment with the power supplied from the electric power system, an inverter is included in the storage battery equipment. Specifically, the inverter converts direct current (DC) power extracted from the storage battery into alternating current (AC) power. Further, a converter is included between the storage battery and the inverter. Here, the converter extracts the DC power from the storage battery and converts the voltage of the DC power.
The storage battery equipment includes a controller that controls the overall operation of the storage battery equipment. The controller periodically sets a target value (i.e., an electric power amount) for the electric power that should be supplied from the storage battery equipment to the building, such that the electric power supplied from the electric power system is efficiently leveled. Further, in some cases, this controller may be in the form of a high level controller that is separate from the storage battery equipment.
In a conventional storage battery equipment, the controller controls the converter such that the amount of electric power actually extracted from the storage battery (or if there are multiple storage batteries, the total amount of electric power extracted from each battery) matches the above described target value.